[C320-list] Vent cowls on boat stern

[MICHAEL COLE]

 I have just moved my boat onto a club mooring in Watson's Bay Sydney.
    In less than a week I have had  the starboard one of the two vents on the stern smashed by the protruding end of a dismasted and unused yacht on a nearby mooring. needless to say I'm getting my mooring moved  about 3-4 metres to the northeast which will eliminate the problem.
   I have two questions :
      1) What exactly do these 2  vents  (if thats what they are)   do?
       2)   Where can I get relacements?   I'm sure I'll have to import them from the States
               Thank You
     Mike Cole    #421   "Mio Dio"
           Sydney